LEDs (Light Emitting Diode) are widely applied in the electronic display devices because of small size, low power consumption, high luminous efficiency, long life and so on. Analog dimming method and PWM (Pulse Width Modulation) dimming method are the conventional ways applied in a LED controller, and the PWM dimming method which modulates the pulse width of a dimming control signal to adjust brightness of LEDs is applied more widely today. In conventional PWM dimming method, usually one dimming control signal controls a plurality of LED strings. As a result, the brightness of the LEDs changes too sharply between ON and OFF, which reduces image quality. Meanwhile, the plurality of output dimming control signals which respectively controls the LED strings may be phase shifted compared with the input dimming control signal, but the duty cycle of them could not be adjusted.
The present invention pertains to provide a phase-shift dimming circuit which generates a plurality of phase-shifted output dimming control signals. Moreover, the duty cycle of the plurality of output dimming control signals may be controlled to be changed.